1. Field of the Invention
The present invention relates to an apparatus and a method for treating organic waste air. More particularly, the present invention relates to an apparatus and a method for UV oxidation and microbiological decomposition of organic waste air.
2. Description of the Related Arts
Organic waste air or organic off-gas means waste air containing organic pollutants. There are several common ways to treat volatile organic waste air in industry, including liquid adsorption, carbon adsorption, thermal incineration., catalytic incineration and bio-decomposition.
Liquid (e.g. basic aqueous solution) is employed in the method of liquid adsorption and activated carbon is employed in carbon adsorption. Organic waste air is then turned from gas form into liquid or solid form by means of its solubility or adsorbability into the liquid or activated carbon. Therefore, organic pollutants having different physical and chemical properties will have different removal efficiencies depending on the solubility of the liquid used or the adsorbability of the organic pollutants by activated carbon. In either case, the organic pollutants dissolved into the liquid or adsorbed into the activated carbon create a second set of contaminants that need to be treated in another way.
For example, carbon adsorption provides a temporary solution by transferring pollutants to the carbon surface, but fails to ultimately eliminate them. The spent carbon must be replaced or regenerated once it is saturated. On-site carbon regeneration may be accomplished by steam desorption or vacuum desorption, but both are cost-ineffective due to excessive energy consumption.
Another common method is thermal incineration, which is normally extremely energy intensive, requiring a nominal combustion temperature between 650xc2x0 C. to 850xc2x0 C. Typical levels of organic pollutant contained in common off-gas do not possess the required oxidation energy to sustain this temperature range. Therefore, the thermal incineration, even equipped with a heat transfer device, would demand a large quantity of auxiliary fuel.
Yet another common method is catalytic incineration, which involves precious or alkali metal as catalysts to lower the activation energy for combustion, consequently reducing the fuel cost needed for thermal incineration. Catalytic incineration is generally more cost effective than thermal incineration in treating organic pollutants at low concentration. However, due to its sensitivity to pollutant-laden air stream and process operating characteristics, the type of catalysts dictates the optimum operating conditions and lifespan of catalysts. Common catalysts deactivation problems (e.g. catalyst poisoning, masking, and fouling) are encountered due to chemical and physical interference by the impurities contained in the off-gas.
Still another common method is bio-decomposition. During the past decade, vapor-phase biofiltration has gained attention for both odor and organic pollutant control, mainly because of its efficiency and its low operating cost. In a biofilter, natural media such as peat, soil, and compost which contain indigenous microorganisms and essential nutrients, provide a natural environment for microorganisms to grow using (for example, organic pollutant) as carbon and energy source. However, these biofiltration systems are susceptible to both toxicity and excessive pollutant concentration. Consequently, pollutant emissions with highly fluctuating influent concentrations render this method questionable.
It is therefore a primary objective of the present invention to provide a new air pollution technology which offers both technical and economical advantages over the conventional methods described above.
To accomplish the above objective, the present invention provides a method for UV oxidation and microbiological decomposition of organic waste air, the method including (a) irradiating organic waste air with ultraviolet (UV) light, wherein the organic pollutants in the waste air undergo oxidation reaction; and (b) polishing the organic pollutant residuals with microorganisms.
The present invention further provides an apparatus for UV oxidation and microbiological decomposition of organic waste air, the apparatus including: a UV oxidation reactor having a UV lamp for irradiating organic pollutants; a humidifier for humidifying the organic waste air; an acid neutralizing device for neutralizing the acidity of the organic waste air; a biofilter containing mixtures of a support material and biosolids, wherein the biosolids contain microorganisms capable of metabolizing or biodegrading one or more of the organic pollutants and the support material is selected from the group consisting of yard waste, compost, activated carbon, molecular sieve and adsorbent; and a monitoring device for detecting the concentration of the organic pollutants.
Alternatively, the present invention also provides an apparatus for UV oxidation and microbiological decomposition of organic waste air, the apparatus including: a UV oxidation reactor having a UV lamp for irradiating organic pollutants; a biotrickling filter containing mixtures of a support material and biosolids, wherein the biosolids contain microorganisms capable of metabolizing or biodegrading one or more of the organic pollutants and the support material is selected from the group consisting of yard waste, compost, activated carbon, molecular sieve and adsorbent; a nutrient reservoir for supplementing the microorganisms with nutrition and water; a pH-monitoring device for monitoring the pH of the nutrient solution; an acid neutralizing device for neutralizing the acidity of the organic waste air; and a monitoring device for detecting the concentration of the organic pollutants.